Google won't help me, I hope someone here can. Fire, Ashes Winter uhh

After seeing all the threads people made because they forgot a book I feel a little disheartened...but who knows! Here goes.

Fantasy of a world of people who exploit this fire stone, so the sky turns to ash. These people have never seen the sky. Some people are forced to mine, who I think don't have magic to tap into this fire stone, while others, who I think can tap into the magic of the fire stone, live in luxury.

Main character is a woman, I think, who was a miner but was found to have the magic. She was taken and I don't remember the rest. What I do remember is the magic rocks of fire, and a really cool little italicized description of what happened to the world because the stone was exploited so much.

I'm done searching, I leave it to you.

Reminds me of The Last Book in the Universe, which is a great book btw.

The description of The Light Ages seems identical to the book I was looking for, thank you.

Only I wrote a report about the book in 8th grade English, which for me was year 2000-2001 and the book you offered was published in 2003. I remember sitting on that damn stool and having to read a passage from it. I also don't think the setting was London. Well thank you for trying, back to reading the Black Company.